[patch 2/6] tty: export tty_open_by_driver

[Okash Khawaja <okash.khawaja@gmail.com>]

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This applies on top of the changes already in staging-next branch which allow
kernel access to TTY dev.

Signe-doff-by: Okash Khawaja <okash.khawaja@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

Index: linux-staging/drivers/tty/tty_io.c
===================================================================
--- linux-staging.orig/drivers/tty/tty_io.c
+++ linux-staging/drivers/tty/tty_io.c
@@ -1369,7 +1369,10 @@ static struct tty_struct *tty_driver_loo
 	struct tty_struct *tty;
 
 	if (driver->ops->lookup)
-		tty = driver->ops->lookup(driver, file, idx);
+		if (!file)
+			tty = ERR_PTR(-EIO);
+		else
+			tty = driver->ops->lookup(driver, file, idx);
 	else
 		tty = driver->ttys[idx];
 
@@ -2001,7 +2004,7 @@ static struct tty_driver *tty_lookup_dri
 		struct tty_driver *console_driver = console_device(index);
 		if (console_driver) {
 			driver = tty_driver_kref_get(console_driver);
-			if (driver) {
+			if (driver && filp) {
 				/* Don't let /dev/console block */
 				filp->f_flags |= O_NONBLOCK;
 				break;
@@ -2034,7 +2037,7 @@ static struct tty_driver *tty_lookup_dri
  *	  - concurrent tty driver removal w/ lookup
  *	  - concurrent tty removal from driver table
  */
-static struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
+struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
 					     struct file *filp)
 {
 	struct tty_struct *tty;
@@ -2079,6 +2082,7 @@ out:
 	tty_driver_kref_put(driver);
 	return tty;
 }
+EXPORT_SYMBOL(tty_open_by_driver);
 
 /**
  *	tty_open		-	open a tty device
Index: linux-staging/include/linux/tty.h
===================================================================
--- linux-staging.orig/include/linux/tty.h
+++ linux-staging/include/linux/tty.h
@@ -401,6 +401,8 @@ extern struct tty_struct *get_current_tt
 /* tty_io.c */
 extern int __init tty_init(void);
 extern const char *tty_name(const struct tty_struct *tty);
+extern struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
+		struct file *filp);
 #else
 static inline void console_init(void)
 { }